A microtome is a piece of precision equipment having a cutting blade for making very thin sections (1 to 15 .mu.m) from organic tissue specimens for pathological examination. Various known microtomes have means for moving the tissue specimen and/or the cutting blade relative to each other in the direction towards and away from the cutting edge of the blade to allow intersection of the specimen with the cutting edge. Known microtomes also provide means for advancing the tissue specimen and/or the blade in a direction perpendicular to the face of the blade to allow the thickness of the slices to be controlled and to prevent contact between the specimen and the blade between cuts. Known microtomes, however, do not provide for relative movement of the blade or tissue specimen in a third direction parallel to the length of the cutting blade.
One known shortcoming of known microtomes is that consecutively sliced organic tissue sections generated at the same position along the length of the blade tend to overlap each other to form ribbons of individual tissue sections, separation of which is often tedious and time consuming. In the past, when invasive techniques involving the use of a scalpel were used by doctors to obtain samples for pathological examination, large samples of diagnostic material was routinely available and separation of each consecutively cut tissue section was less critical. With the advent of modern less-invasive methods for obtaining organic tissue specimens involving "skinny needle biopsies" and the use of fiber optic instruments, however, pathologists are often presented with tissue specimens of from about 10 to about 50 milligrams of tissue, which are much smaller than the large tissue "hunks" weighing from about 200 to about 2000 milligrams obtained from earlier surgical sampling methods. In order to obtain the maximum amount of information from only a few micro or milligrams of tissue, consecutively cut tissue sections are often treated with different histochemical reagents and histochemical tests are often repeated using slices taken at different depths within the tissue specimen. Thus, there is a currently a need to sort consecutively cut organic tissue sections into separate tissue ribbons and to control the sequence in which consecutively sliced tissue sections are added to each ribbon based on the logic of the histochemical analysis to be performed. Generating multiple tissue ribbons having a controlled sequencing is not possible using known microtomes in which each cut is made at the same position along the length of the cutting blade and only a single ribbon can be generated at a time.
Another known shortcoming of known microtomes providing only two-dimensional movement is that each consecutive intersection of the tissue specimen with the cutting edge of the blade is always made with the same segment of the cutting edge or a limited number of segments depending on the blade length. A typical 120 mm blade would provide an average of about 3 to 5 new cutting surfaces by shifting the blade in its clamp. The blade must be replaced as soon as the operative segments become nicked or dull. Further, known microtome blades are generally clamped into a heavy metal microtome blade carrier that fits properly into the various designs of commercial microtomes. Changing or shifting the blade requires releasing a screw or cam lock device on the blade carrier and disposing the used blade in a proper medical waste container. Changing or shifting the blade thus may be time consuming and requires handling of the blade itself. Since the blades are utilized to cut tissue sections made from potentially contaminated human tissue materials, technicians risk being infected with Hepatitis, AIDS, Tuberculosis or similar diseases by bacteria and viruses present on the cutting edge of the used blades.
Thus there is also a need to reduce the frequency of blade changes by providing a microtome cutting blade that is capable of being advanced in the direction parallel to the length of the blade to provide a fresh portion of the cutting edge at the cutting area of the microtome when the operative segment of the cutting edge becomes nicked or dull. There is a further need to provide a microtome cutting blade which is housed in a chamber or cartridge which may be disposed of in a contaminated medical waste system without exposing the technician to the cutting edge of the blade.
It is an object of the present invention to provide a method for automatically sorting tissue sections consecutively cut in a microtome from a tissue specimen into a plurality of tissue ribbons. Another object of the present invention is to provide a microtome having a cutting blade which is advanceable in the direction parallel to the direction of the length of the blade to expose a fresh segment of the cutting edge to the cutting area of the microtome.
A further object of the present invention is to provide an advanceable microtome cutting blade cartridge system which protects technicians from exposure to the cutting edge of the blade during handling.